docs: Fix executor plugin example in docs

[dinever]

Signed-off-by: Peixuan Ding [email protected]

Hi, I've been trying the executor plugin and found several issues with the docs. This PR fixes them. Please see the inline comments for more details.

Thanks!

[dinever]

container is defined under sidecar:

argo-workflows/pkg/plugins/spec/plugin_types.go

Lines 23 to 29 in 774bf47

	type PluginSpec struct {
	Sidecar Sidecar `json:"sidecar"`
	}
	type Sidecar struct {
	Container apiv1.Container `json:"container"`
	}

[dinever]

securityContext, resources are mandatory:

argo-workflows/pkg/plugins/spec/plugin_types.go

Lines 36 to 44 in 774bf47

	if c.Resources.Requests == nil {
	return fmt.Errorf("resources requests are mandatory")
	}
	if c.Resources.Limits == nil {
	return fmt.Errorf("resources limits are mandatory")
	}
	if c.SecurityContext == nil {
	return fmt.Errorf("security context is mandatory")
	}

[alexec]

🚀 LGTM!